We did not have a problem changing from Taca to Copa at MGA. The trick was we told a person there before we got to immigration, as we were walking up the walkway. That person took us through a door (bypassing immagration) and to the gate. They had us wait in the bording area and had an agent bring up the passes. (in some cases it helps to speak spanish.) But for all of our connections we tried to let everyone know when we did not have boarding passes. They always went to get them for us.
We did not have to pay departure tax on any of our connecting flights. In Bogota if you stay the night be sure to get a slip when you check in for your flight that allows you to pay 1/2 of the departure tax. I think you also save if you pay in pesos. We paid in dollars but found out later that it would have been cheaper to pay in pesos.

[This message has been edited by fabsco (edited 03-15-2000).]